This application relates generally to a single horizontal drive assembly used in a power seat adjuster that provides a stable seat mount due to the use of a truss structure extending between seat track assemblies.
Seat track arrangements for mounting seats within vehicles are generally well known. Most arrangements provide for a seat to be moved or adjusted in forward and rearward directions within a vehicle along inboard and outboard track assemblies. The inboard track assembly is spaced apart from the outboard track assembly and both track assemblies include a first track member that is mounted to the vehicle and a second track member that is supported for movement relative to the first track member. The first and second track members are usually mounted in a horizontal configuration with bearing members located on the sides of the first and second tracks. The seat is adjusted in forward and rearward directions by sliding the second track members relative to the first track members along the bearing members.
Known power seat adjusters use a motor drive assembly including at least one bi-directional electric motor that rotates a pair of drive shafts extending outwardly from the motor to a gear assembly mounted on each of the second track members. In one known configuration, threaded shafts are mounted to the second track and extend longitudinally between the first and second tracks for both the inboard and outboard track assemblies. The motor drives the gear assembly and each gear assembly rotates its respective threaded shaft. A drive block or nut is mounted to each of the first tracks and threadingly receives the threaded shaft to cause reciprocal horizontal movement of the second track upon selective receipt of power from the motor and drive shafts.
One disadvantage of this known configuration is that two gear boxes are needed, two threaded shafts are needed, and two drive blocks are needed. The duplication of identical components increases the weight and the cost and requires a significant amount of packaging space.
Another disadvantage of having two threaded shafts, one mounted on the inboard track assembly and one mounted on the outboard track assembly, is that the shafts are difficult to synchronize, i.e., one threaded shaft is at one horizontal position while the other threaded shaft is at a different horizontal position. This can cause the seat to be misaligned within the vehicle, which is undesirable. Thus, assembly cost is high because it is difficult to assemble the seat adjuster such that the rotation of the inboard threaded shaft exactly corresponds to the outboard threaded shaft.
Another disadvantage with this known configuration is the difficulty of packaging the threaded shafts between the first and second track members in each of the inboard and outboard track assemblies. This configuration requires the track members to be large in order to accommodate the threaded shafts and the drive blocks between the two track members. This configuration takes up more packaging space underneath the seat.
Accordingly, it is desirable to provide a power seat adjuster that only has one horizontal drive mechanism mounted to one of the track assemblies to reduce the overall number of components and the overall weight of the seat adjuster, and which includes a drive member that is not centered between first and second track members. It is also desirable to provide a single horizontal drive mechanism with only one driving member for adjusting seat position, but which also provides a stable seat mount.